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-rw-r--r--kernel/irq/ipi-mux.c206
1 files changed, 206 insertions, 0 deletions
diff --git a/kernel/irq/ipi-mux.c b/kernel/irq/ipi-mux.c
new file mode 100644
index 000000000000..fa4fc18c6131
--- /dev/null
+++ b/kernel/irq/ipi-mux.c
@@ -0,0 +1,206 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Multiplex several virtual IPIs over a single HW IPI.
+ *
+ * Copyright The Asahi Linux Contributors
+ * Copyright (c) 2022 Ventana Micro Systems Inc.
+ */
+
+#define pr_fmt(fmt) "ipi-mux: " fmt
+#include <linux/cpu.h>
+#include <linux/init.h>
+#include <linux/irq.h>
+#include <linux/irqchip.h>
+#include <linux/irqchip/chained_irq.h>
+#include <linux/irqdomain.h>
+#include <linux/jump_label.h>
+#include <linux/percpu.h>
+#include <linux/smp.h>
+
+struct ipi_mux_cpu {
+ atomic_t enable;
+ atomic_t bits;
+};
+
+static struct ipi_mux_cpu __percpu *ipi_mux_pcpu;
+static struct irq_domain *ipi_mux_domain;
+static void (*ipi_mux_send)(unsigned int cpu);
+
+static void ipi_mux_mask(struct irq_data *d)
+{
+ struct ipi_mux_cpu *icpu = this_cpu_ptr(ipi_mux_pcpu);
+
+ atomic_andnot(BIT(irqd_to_hwirq(d)), &icpu->enable);
+}
+
+static void ipi_mux_unmask(struct irq_data *d)
+{
+ struct ipi_mux_cpu *icpu = this_cpu_ptr(ipi_mux_pcpu);
+ u32 ibit = BIT(irqd_to_hwirq(d));
+
+ atomic_or(ibit, &icpu->enable);
+
+ /*
+ * The atomic_or() above must complete before the atomic_read()
+ * below to avoid racing ipi_mux_send_mask().
+ */
+ smp_mb__after_atomic();
+
+ /* If a pending IPI was unmasked, raise a parent IPI immediately. */
+ if (atomic_read(&icpu->bits) & ibit)
+ ipi_mux_send(smp_processor_id());
+}
+
+static void ipi_mux_send_mask(struct irq_data *d, const struct cpumask *mask)
+{
+ struct ipi_mux_cpu *icpu = this_cpu_ptr(ipi_mux_pcpu);
+ u32 ibit = BIT(irqd_to_hwirq(d));
+ unsigned long pending;
+ int cpu;
+
+ for_each_cpu(cpu, mask) {
+ icpu = per_cpu_ptr(ipi_mux_pcpu, cpu);
+
+ /*
+ * This sequence is the mirror of the one in ipi_mux_unmask();
+ * see the comment there. Additionally, release semantics
+ * ensure that the vIPI flag set is ordered after any shared
+ * memory accesses that precede it. This therefore also pairs
+ * with the atomic_fetch_andnot in ipi_mux_process().
+ */
+ pending = atomic_fetch_or_release(ibit, &icpu->bits);
+
+ /*
+ * The atomic_fetch_or_release() above must complete
+ * before the atomic_read() below to avoid racing with
+ * ipi_mux_unmask().
+ */
+ smp_mb__after_atomic();
+
+ /*
+ * The flag writes must complete before the physical IPI is
+ * issued to another CPU. This is implied by the control
+ * dependency on the result of atomic_read() below, which is
+ * itself already ordered after the vIPI flag write.
+ */
+ if (!(pending & ibit) && (atomic_read(&icpu->enable) & ibit))
+ ipi_mux_send(cpu);
+ }
+}
+
+static const struct irq_chip ipi_mux_chip = {
+ .name = "IPI Mux",
+ .irq_mask = ipi_mux_mask,
+ .irq_unmask = ipi_mux_unmask,
+ .ipi_send_mask = ipi_mux_send_mask,
+};
+
+static int ipi_mux_domain_alloc(struct irq_domain *d, unsigned int virq,
+ unsigned int nr_irqs, void *arg)
+{
+ int i;
+
+ for (i = 0; i < nr_irqs; i++) {
+ irq_set_percpu_devid(virq + i);
+ irq_domain_set_info(d, virq + i, i, &ipi_mux_chip, NULL,
+ handle_percpu_devid_irq, NULL, NULL);
+ }
+
+ return 0;
+}
+
+static const struct irq_domain_ops ipi_mux_domain_ops = {
+ .alloc = ipi_mux_domain_alloc,
+ .free = irq_domain_free_irqs_top,
+};
+
+/**
+ * ipi_mux_process - Process multiplexed virtual IPIs
+ */
+void ipi_mux_process(void)
+{
+ struct ipi_mux_cpu *icpu = this_cpu_ptr(ipi_mux_pcpu);
+ irq_hw_number_t hwirq;
+ unsigned long ipis;
+ unsigned int en;
+
+ /*
+ * Reading enable mask does not need to be ordered as long as
+ * this function is called from interrupt handler because only
+ * the CPU itself can change it's own enable mask.
+ */
+ en = atomic_read(&icpu->enable);
+
+ /*
+ * Clear the IPIs we are about to handle. This pairs with the
+ * atomic_fetch_or_release() in ipi_mux_send_mask().
+ */
+ ipis = atomic_fetch_andnot(en, &icpu->bits) & en;
+
+ for_each_set_bit(hwirq, &ipis, BITS_PER_TYPE(int))
+ generic_handle_domain_irq(ipi_mux_domain, hwirq);
+}
+
+/**
+ * ipi_mux_create - Create virtual IPIs multiplexed on top of a single
+ * parent IPI.
+ * @nr_ipi: number of virtual IPIs to create. This should
+ * be <= BITS_PER_TYPE(int)
+ * @mux_send: callback to trigger parent IPI for a particular CPU
+ *
+ * Returns first virq of the newly created virtual IPIs upon success
+ * or <=0 upon failure
+ */
+int ipi_mux_create(unsigned int nr_ipi, void (*mux_send)(unsigned int cpu))
+{
+ struct fwnode_handle *fwnode;
+ struct irq_domain *domain;
+ int rc;
+
+ if (ipi_mux_domain)
+ return -EEXIST;
+
+ if (BITS_PER_TYPE(int) < nr_ipi || !mux_send)
+ return -EINVAL;
+
+ ipi_mux_pcpu = alloc_percpu(typeof(*ipi_mux_pcpu));
+ if (!ipi_mux_pcpu)
+ return -ENOMEM;
+
+ fwnode = irq_domain_alloc_named_fwnode("IPI-Mux");
+ if (!fwnode) {
+ pr_err("unable to create IPI Mux fwnode\n");
+ rc = -ENOMEM;
+ goto fail_free_cpu;
+ }
+
+ domain = irq_domain_create_linear(fwnode, nr_ipi,
+ &ipi_mux_domain_ops, NULL);
+ if (!domain) {
+ pr_err("unable to add IPI Mux domain\n");
+ rc = -ENOMEM;
+ goto fail_free_fwnode;
+ }
+
+ domain->flags |= IRQ_DOMAIN_FLAG_IPI_SINGLE;
+ irq_domain_update_bus_token(domain, DOMAIN_BUS_IPI);
+
+ rc = irq_domain_alloc_irqs(domain, nr_ipi, NUMA_NO_NODE, NULL);
+ if (rc <= 0) {
+ pr_err("unable to alloc IRQs from IPI Mux domain\n");
+ goto fail_free_domain;
+ }
+
+ ipi_mux_domain = domain;
+ ipi_mux_send = mux_send;
+
+ return rc;
+
+fail_free_domain:
+ irq_domain_remove(domain);
+fail_free_fwnode:
+ irq_domain_free_fwnode(fwnode);
+fail_free_cpu:
+ free_percpu(ipi_mux_pcpu);
+ return rc;
+}